Re: how to optimise further

The results of different types of optimization vary for AdWords account, and it's a bit trickier to offer worthwhile suggestions without access to your account. However, here are a few general ideas for your consideration (in alphabetical order, not importance):

Audiences

For remarketing lists, consider testing ad frequency, how soon ads begin serving, and when the cookie falls out of the remarketing list. For example, do most remarketing conversions happen within the first few days after the cookie is added to the list? Then it may not make sense to keep serving ads for a longer period of time for users that aren't very likely to convert.

Delivery Method

Standard delivery throttles your ad in the early parts of the day if you're likely to run out of budget. If that's not a concern for you, accelerated delivery may be a good idea to serve on all relevant queries.

Analyzing age & gender campaign and ad group performance might help you determine if optimizing these segments would provide any campaign or ad group performance improvements. You might choose to adjust bids for certain segments or exclude a segment that doesn't meet campaign objectives.

If certain device types (mobile, tablets, or computers) don't directly or indirectly result in conversions, you may want to adjust bids to -100% for that type of device.

Conversely, if you find that a certain device performs very well and there's leeway to increase the budget or cost per conversion, you may want to increase bids on that type of device.

Extensions

Review the list of ad extensions in AdWords and add the ones that are relevant to your campaign or campaigns.

Landing pages

If your website has multiple relevant pages, consider testing how each landing page performs by creating duplicate ads with different URLs (or run an experiment).

Location targeting

It may be helpful to create a geo location report to determine which areas are performance outliers (both those that perform well and those that perform poorly). Add those locations to the targeting and make bid adjustments.

Tools

Optimize based on the attribution models (inside AdWords, click "Tools" > "Attribution" and view the attribution reports in the left menu).

As I previously mentioned, every account is different and results vary. I hope these ideas help get the ball rolling for continuing to optimize your account.